Title | Source, timing, frequency and flux of ice-rafted detritus to the Northeast Atlantic margin, 30–12 ka: testing the Heinrich precursor hypothesis |
Publication Type | Journal Article |
Year of Publication | 2010 |
Authors | Haapaniemi, AI, Scourse, JD, Peck, VL, Kennedy, H, Kennedy, P, Hemming, SR, Furze, MFA, PieńKowski, AJ, Austin, WEN, Walden, J, Wadsworth, E, Hall, IR |
Journal | Boreas |
Volume | 39 |
Pagination | 576-591 |
ISBN Number | 1502-3885 |
Abstract | Increased fluxes of ice-rafted detritus (IRD) from European ice sheets have been documented some 1000–1500 years before the arrival of Laurentide Ice Sheet (LIS)-sourced IRD during Heinrich (H) events. These early fluxes have become known as ‘precursor events’, and it has been suggested that they have mechanistic significance in the propagation of H events. Here we present a re-analysis of one of the main cores used to generate the precursor concept, OMEX-2K from the Goban Spur covering the last 30 ka, in order to identify whether the British–Irish Ice Sheet (BIIS) IRD fluxes occur only as precursors before H layers. IRD characterization and planktonic foraminiferal δ18O measurements constrained by a new age model have enabled the generation of a continuous record of IRD sources, timing, frequency and flux, and of local contemporary hydrographic conditions. The evidence indicates that BIIS IRD precursors are not uniquely, or mechanistically, linked to H events, but are part of the pervasive millennial-scale cyclicity. Our results support an LIS source for the IRD comprising H layers, but the ambient glacial sections are dominated by assemblages typical of the Irish Sea Ice Stream. Light isotope excursions associated with H events are interpreted as resulting from the melting of the BIIS, with ice-sheet destabilization attributed to eustatic jumps generated by LIS discharge during H events. This positive-feedback mechanism probably caused similar responses in all circum-Atlantic ice-sheet margins, and the resulting gross freshwater flux contributed to the perturbation of the Atlantic Meridional Overturning Circulation during H events. |
URL | http://dx.doi.org/10.1111/j.1502-3885.2010.00141.x |
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